Geological and Geochemical Characteristics of the Geothermal Resources in Rucheng, China

Abstract

The development of geothermal energy promotes the changing of energy consumption structure in China. A series of experiments were performed to evaluate the geothermal resources of Rucheng County, which is the largest geothermal field in Central South China. The experiments include geothermal exploration, apparent resistivity, and determining the geochemical characteristics of the geothermal water. The experimental results show that the F3 fault zone and F1 hanging wall secondary fault are the main thermal control, heat conduction, water diversion, and thermal storage structures. The pH, EC, and Eh of the river water, shallow groundwater, and geothermal water exhibit seasonal changes. The pH and EC of the geothermal water are higher than those of the river water and shallow groundwater, while the Eh is lower. In addition, the corrosivity coefficient Kk and the Ryznar index are used to evaluate the corrosivity and calcium carbonate scaling of the geothermal water, and it is found that the geothermal water has no corrosiveness or calcium carbonate scaling, which indicates that the geothermal energy in Rucheng County has wide application prospects.

Implications of Local‐Scale Approximations on Describing Fluid Flow in Rock Fractures With Stress‐Induced Void Heterogeneity

“…In addition to the bulk fracture transmissivity, an accurate aperture‐averaged local velocity (referred to as velocity in this section for simplicity) field is important to study flow related‐processes such as mass transport and heat transfer in fractured rocks (Neuman, 2005; Long, et al., 2021), especially when the flow field is heterogenous due to the complex fracture void structure. Therefore in this section, the spatial distributions of local velocity deviation ( D v = 1− v LA / v × 100%, where v and v LA are the local velocity obtained from the NSE and from applying local‐scale approximations, respectively) were obtained for the RE using local‐scale approximations OR, GE, JH, BT, and PS in F1 as shown in Figure 8.…”

“…In addition to the bulk fracture transmissivity, an accurate aperture-averaged local velocity (referred to as velocity in this section for simplicity) field is important to study flow related-processes such as mass transport and heat transfer in fractured rocks (Neuman, 2005;Long, et al, 2021), especially when the flow field is heterogenous due to the complex fracture void structure. Therefore in this section, the spatial distributions tively, the extent of local aperture variation relative to local length, the extent of local aperture variation relative to local aperture, and the extent of geometric asymmetry relative to local length, by which the geometry of a local wedge can be completely determined (Wang et al, 2020).…”

Hydrothermal Systems Characterized by Crustal Thermally‐dominated Structures of Southeastern China

“…Geothermal anomalies in South Jiangxi are associated with regional faults of NNE and NEE directions, with discharge temperatures ranging from 26-88°C (Sun et al, 2014). Thermal springs in south Hunan reach 91.5°C and are mainly controlled by NEoriented faults (Long et al, 2021). The early Paleozoic belt with Triassic overprint region is characterized by Cenozoic large-scale basaltic magmatic activity developed in the Leizhou Peninsula (LP) and northern Hainan (Tian et al, 2020;Hu et al, 2022).…”

“…As a result, the circulation depth of the hydrothermal system gradually becomes reduced and the temperature of the geothermal reservoir gradually decreases. The formation of inland medium-temperature hydrothermal systems, such as Rucheng, is speculated to be due to the increase in fault scale under local geological stresses, that may be caused by the increase in the depth of water circulation (Long et al, 2021).…”

Fracture Characteristics and Heat Accumulation of Jixianian Carbonate Reservoirs in the Rongcheng Geothermal Field, Xiong'an New Area

“…As one of the important substitutes for fossil fuels, geothermal energy is a green, low-carbon and recyclable renewable energy source. It has the characteristics of large reserves, wide distribution, clean and a high utilization rate (Fridleifsson, 2001;Axelsson, 2012;Ghassemi, 2012;Guo and Li, 2013;Long et al, 2019Long et al, , 2021. The exploitation and utilization of geothermal resources are not only a necessary means to alleviate haze and control air pollution, but also an effective way to adjust the energy structure and fulfill carbon discharges reduction (Wang G et al, 2018a;Wang S et al, 2018;Wu et al, 2018;Guo et al, 2019).…”